1. Field of the Invention
This invention relates to an image forming apparatus. More particularly, this invention relates to an ink-jet type image forming apparatus in which an image is formed by ejecting ink onto a recording medium such as paper.
2. Description of Related Art
Conventionally, an ink-jet type image forming apparatus includes, for example, a recording medium transfer member that transfers paper and the like in a specified transfer direction and a recording head carriage arranged opposite a transfer path of the recording medium. The carriage is movable in a direction perpendicular to the transfer direction of the recording medium and ejects ink from nozzles toward the transfer path of the recording medium.
Moreover, a full color ink-jet type image forming apparatus uses a recording head carriage capable of ejecting yellow, magenta, cyan and black inks. Further, the full color ink-jet type image forming apparatus generally comprises a plurality of nozzle components for each respective color, and a plurality of ink tanks that supply ink to the nozzle components. Moreover, each of the nozzle components has a plurality of nozzles formed therein and each of the ink tanks is designed to be attachable to and detachable from the recording head carriage.
The ink-jet type image forming apparatus carries the recording medium by the recording medium transfer member. An image is formed on the recording medium by ejecting ink onto the recording medium in accordance with the prescribed image information while the recording medium is being transferred and the recording head carriage is being moved back-and-forth across the transfer path.
However, this type of ink-jet type image forming apparatus has various problems in maintaining image quality. Poor image quality is associated with the ink itself, as well as the ink being ejected from the nozzles to form an image.
Specifically, in the aforementioned ink-jet type image forming apparatus, first, the ink in the nozzle is known to quickly dry out when images are not being formed. When this condition occurs, the viscosity of the ink increases, thereby changing the way the ink ejects from the nozzle components, such that the desired image is not properly formed.
Second, when foreign material or air enters the nozzles, or when the drying of the ink has progressed, the ink does not properly eject.
Third, it is known that the ejection of the ink occasionally is not stable and the image cannot properly be formed because the surface of the ink dries immediately after image forming begins.
Therefore, the established practice to overcome the above-mentioned problems in a conventional ink-jet type image forming apparatus is to provide a plurality of cap members to prevent the ink from drying by covering the nozzles when images are not being formed. Also, a pump member is added for suctioning ink from the cap members while an expelled ink tank stores the expelled ink held by the cap members. The aforementioned solutions are disclosed in Japanese Laid-Open Patent Publications 6-226995, 4-45953 and 60-145854.
Also, during a capping stage, the drying of ink in the ink-jet type image forming apparatus is prevented by covering each nozzle with a respective cap member. Sticky ink can also be removed from each nozzle by suctioning the ink when the nozzles are covered by their respective cap members. Further, during a dummy jet stage, the ejection blurring of ink that occurs during the beginning of image formation can be prevented in advance by ejecting the ink from each nozzle prior to initiating image formation. Moreover, during a recovery stage the ink-jet type image forming apparatus suctions the expelled ink held by each cap member during each of these operations and stores the expelled ink in an expelled ink tank.
However, in order for the expelled ink to properly flow from the cap member to the expelled ink tank in these ink-jet type image forming apparatus, it became necessary to form the expelled ink flow entry port on top of the expelled ink tank, and to set the direction of the ink expulsion flowpath in a vertical or inclined direction.
Consequently, because it was necessary to preserve the height from the top end of the recording head to the bottom end of the expelled ink tank, it was not possible to miniaturize the apparatus by making it thinner. This was due to the fact that the height in the ink-jet type image forming apparatus, measured from the top end of the cap member to the bottom end of the expelled ink tank, was typically designed so that the cap member was arranged opposite to the recording head.